Low herbs with alternate entire leaves and terminal clusters of small greenish-white bell-shape flowers without petals in spring and early summer.
Parasitic plants, attached to the branches of trees.
Flowers greenish-brown or reddish-brown, at or near the ground, with inferior 6-celled ovary.
Herbs with alternate entire leaves, stipules surrounding the stem above the base of each leaf, and small green, white or pink flowers without petals.
Herbs, with inconspicuous greenish or reddish flowers without petals, in summer.
Herbs, with alternate leaves, and inconspicuous greenish or reddish flowers without petals, which are axillary or in dense clusters, blooming in summer.
Herbs with alternate entire leaves, small flowers without petals, and a many-celled ovary.
Herbs, with opposite entire leaves and flowers in small clusters surrounded by a broad open calyx-like involucre; the true calyx colored like a corolla; petals none (4-8 dm. high; flowers purple, in summer).
Herbs, with opposite entire leaves, and minute flowers without petals. (Prostrate spreading or freely branched plants, 3 dm. high or less; flowers in summer.)
Prostrate herbs, with whorled leaves and small whitish axillary flowers without petals, in summer.
Herbs, with opposite or whorled entire leaves, and stems frequently swollen at the nodes. Sepals 4 or 5; petals separate, as many as the sepals, or rarely none; stamens twice as many as the petals in plants with conspicuous flowers, sometimes fewer in those with small flowers; ovary 1-celled, with the ovules on a central axis, and with 2-5 styles.
Herbs with opposite or alternate leaves and regular flowers with 2 sepals, 5 petals, and a 1-celled ovary with 2 or 3 styles.
Submerged aquatics, with whorled, finely dissected leaves and inconspicuous flowers with neither calyx nor corolla.
Aquatic plants, with usually large and floating leaves which are round or elliptical and palmately veined.